JPH03287135A - Organic nonlinear optical material - Google Patents

Abstract

PURPOSE:To obtain a single crystal which is stable at room temp., is excellent in resistance to optical damaging and has no inverse symmetric center by constituting the single crystal of specific p-acetoamide cinnamic acid. CONSTITUTION:The single crystal is constituted of the p-acetoamide cinnamic acid expressed by formula I. The p-acetoamide cinnamic acid has good crystallinity and the single crystal is easily obtd. by a slow evaporation method from an org. solvent, etc. The fine crystal powder of the p-acetoamide cinnamic acid exhibits the second harmonic wave generating (SHG) efficiency equiv. to the second harmonic wave generating efficiency of urea. The org. nonlinear material which is stable at room temp., has the good crystallinity, is white and highly transparent, has the cut off wavelength existing in a short wavelength region and has the excellent resistance to optical damaging is obtd. in this way.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an organic nonlinear material used as a light control element in a wide range of fields such as optical computers and optical communications. The present invention relates to an organic nonlinear optical material that is in the region, exhibits good SHG activity, has good crystallinity, and has excellent light damage resistance.

[Conventional technology]

Nonlinear optical materials produce phenomena such as frequency conversion, amplification, oscillation, and switching of laser light, and generate second harmonics (
It can be applied to SHG), third harmonic generation (THG), high-speed shutter, optical memory, optical arithmetic element, etc. In this way, nonlinear optical materials have the function of converting optical frequencies and can be applied to optical switches that take advantage of the property that the refractive index changes depending on the electric field, so active research is progressing. It is being

Conventionally, water-soluble KH2P has mainly been used as a nonlinear optical material.
Inorganic single crystal materials (dielectric crystals) such as O, (KDP), NH4H2PO4, or water-insoluble LtNbo, KNbOs are used, and examples of practical use include, for example, conversion of KDP. The second harmonic generation of a powerful YAG laser is used as a material, and it is used as a short wavelength laser driver for inertial nuclear fusion, a dye laser excitation light source for uranium separation, etc.

On the other hand, recently, urea, p-nitroaniline, 2-methyl-4-nitroaniline (MNA), 4'-nitroaniline (MNA), 4-(N), etc.

N-dimethylamino)-4'-nitrostilbene (DA
Development of organic nonlinear optical materials such as NS) is progressing. Regarding polymer materials such as polydiacetylene and polyvinylidene fluoride, we can utilize their nonlinear optical effects to
Applications to waveguides with control functions, optical ICs, etc. are being considered.

Organic nonlinear optical materials generally have nonlinearity originating from intramolecular π electrons or intermolecular charge transfer, so they do not involve lattice vibration in response to light, and therefore have a faster response than inorganic materials. It is possible to synthesize materials with large optical constants and materials with variable absorption regions. In addition, various methods such as LB film, vapor deposition, liquid crystal formation, polymerization, etc. are conceivable as a method of forming a material into an element, in addition to single crystallization.

For recent research results on nonlinear optical materials, see e.g.
``Organic nonlinear optical materials'' supervised by Kato and Nakanishi (CM;
S CHEMLA, Spear, S CHEMLA, Published in 1985)
J, ZYSS edition “Non1inear 0ptical
Pr.

"Perties and Crystals" Vol.
, I, Vol., TI, etc.

By the way, nonlinear optical materials are generally required to have the following characteristics.

(1) Among nonlinear optical effects, especially second harmonic generation (S
HG) is positioned as a basic technology for wavelength conversion due to its high conversion efficiency, and SHG efficiency (1
The relative intensity of the second harmonic is required to be high.

(2) In order to produce second-order nonlinear optical effects such as SHG, it is necessary for the substance to lack a center of inversion symmetry, and when it becomes a crystal, for example, when molecules In practice, it is important to arrange the moments so that they cancel each other out and not end up with a center of inversion symmetry.

(3) It is desired that the material be stable at room temperature and form a single crystal as large as possible.

(4) The wavelength of current semiconductor lasers is about 800 nm, so the maximum wavelength (max) and cutoff wavelength (
(cutoff) is preferably in the short wavelength region as much as possible.

However, in known inorganic nonlinear optical materials, highly pure single crystals are expensive, have deliquescent properties, and generally have lower SHG efficiency than organic materials, and can only convert wavelengths of light within a limited range. The disadvantage is that it is not available.

On the other hand, it is known that some organic nonlinear optical materials generally have high SHG efficiency, but it is difficult to prepare stable and large crystals at room temperature. For example, MNA
Although it has high SHG efficiency, it is difficult to obtain large single crystals. Although urea is easy to obtain large single crystals, is white and transparent, and has a short cutoff wavelength of 200 nm, it has the disadvantage of poor moisture resistance. Further, DANS, which is a stilbene derivative, exhibits a very large second-order nonlinear polarizability β at the molecular level, but when it becomes a crystal, it does not exhibit a nonlinear optical effect because the molecular arrangement has a center of inversion symmetry.

As described above, the conventional technology is still insufficient in providing an organic nonlinear optical material that has high SHG efficiency, is stable, and is easy to grow into a large single crystal.

[Problems to be Solved by the Invention] An object of the present invention is to overcome the problems of the prior art described above, to form a single crystal that is stable at room temperature, has excellent resistance to light damage, and does not have a center of inversion symmetry, and to The object of the present invention is to provide an organic nonlinear optical material that can be grown into a large single crystal according to the requirements, has good SHG efficiency, and has a cutoff wavelength in a short wavelength region.

As a result of intensive research, the present inventors found that p-acetamidocinnamic acid is suitable for the above-mentioned purpose, and based on that knowledge, they completed the present invention.

[Means for solving the problem] That is, according to the present invention, p represented by the following formula [I]
- An organic nonlinear optical material is provided, characterized in that it consists of acetamidocinnamic acid.

Hereinafter, the constituent elements of the present invention will be explained in detail.

[p-acetamidocinnamic acid] The p-acetamidocinnamic acid compound used in the present invention is:
It has good crystallinity, and single crystals can be easily obtained by slow evaporation from organic solvents.

The single crystal is stable at room temperature, is not easily damaged by light, and is easy to process, so it can be easily fabricated into devices.

The crystalline fine powder of p-acetamidocinnamic acid exhibits a good nonlinear optical effect, as is clear from the SHG efficiency of urea ability, and its cutoff wavelength is as short as 380 nm. It can be used as a wavelength conversion element for semiconductor lasers with a wavelength of about 800 nm.

The compound of the present invention can be used as a nonlinear optical material in various forms such as powder, single crystal, and solution.

(Margin below) [Example] The present invention will be specifically described below with reference to Examples.

[Example 1] Nd:YAG laser was applied to fine powder crystals of p-acetamidocinnamic acid manufactured by LANCASTER.
(wavelength = 1.064 μm, output 10 mJ/pulse), a second harmonic was generated (SHG) L, and green light with a wavelength (532 nm) half that of the incident light was observed.

Moreover, its SHG efficiency was comparable to that of urea.

The crystals of this compound were stable at room temperature, had good crystallinity, and showed no optical damage caused by laser light.

From the above facts, it was confirmed that this compound is an excellent organic nonlinear optical material.

〔Effect of the invention〕

According to the present invention, it is possible to provide an organic nonlinear material that is stable at room temperature, has good crystallinity, is white, has excellent transparency, has a cutoff wavelength in a short wavelength region, and has excellent resistance to light damage.

The organic nonlinear optical material of the present invention has important practical significance, such as being able to be used as a wavelength conversion element for a semiconductor laser.

Claims (1)

[Claims] (1) An organic nonlinear optical material characterized by being composed of p-acetamidocinnamic acid represented by the following formula [I] ▲Mathematical formula, chemical formula, table, etc.▼[I].